car heaters question?

mk_wotsit

Is the power for heaters, rear window de-mister, air-con, cd player etc ....FREE power from the battery which charges as you go along anyway, or is it actually using extra petrol?

sammybo22

I think that all the above apart from the Air con runs on battery power, A/C uses fuel.

LesD

Come on all you scientists out there! How about a dissertation on the creation and dissipation of energy?

In the meantime, can we move this to the motoring forum?

uktyler

They use the power from the battery, however they put a higher load on the alternator to charge the battery, using more fuel.
There aew a study done last year, were they tested cars driven with the air con on, and with it off and the windoes open. The cars with air con used less fuel because the windows being closed meant less drag.

mk_wotsit

LesD wrote: »

Come on all you scientists out there! How about a dissertation on the creation and dissipation of energy?

In the meantime, can we move this to the motoring forum?

Beg your pardon....new girl here...this forum is so huge, I didn't see a motoring section!
....so I can relax and turn the heater up full wack then???

moonrakerz

Nothing is FREE !, the battery is charged by an alternator which is driven by a belt off the engine. So even having the radio on will cause a minute increase in fuel consumption.

Mind you, the number of idiots I see driving on no lights/side lights in fog/rain/dark I think a lot of people think the car electrics are powered from the mains at home !

steveo3002

not enough extra fuel used to worry about....save more by sensible driving , pumped up tyres etc

tanith

mk wotsit everything thing that you can turn on and off in your car will in the end cost you more in fuel if you use it than if you don't ..... some things are for your comfort and some for safety , I wouldn't compromise on the safety aspect of things... ie turning on the lights in the dark :T

thescouselander

mk_wotsit wrote: »

Is the power for heaters, rear window de-mister, air-con, cd player etc ....FREE power from the battery which charges as you go along anyway, or is it actually using extra petrol?

Actually, the battery is only there to start the car and temporarily run some devices such as the radio while the engine is off. As soon as you start the engine the alternator takes the load for running anything electrical. If you were to disconnect the battery while the engine is running everything should keep working.

The heater in your car works off the hot coolant in the engine. If it wasn't used to heat the inside the heat would just be radiated outside anyway by the radiator. Of course the fan uses electricity but not that much so generally keeping warm wont cost you that much.

The rear de-mister uses a lot of current (around 30 amps). This puts strain on the alternator therefore the engine will have to do more work. I would suggest only using the de-mister when you need it.

Things such as radios don't use much power

Lights can use a lot especially if your car has a lot of them but as another poster has said safety has to come first so its not a good idea to turn them off to try and save money.

Air con works by directly taking mechanical power from the engine - this causes the engine to use more fuel.

anewman

Yes the fan uses the power, not the heat. So if you can, put the heat on full with the fans, then when the screen is de-misted and the car is warm, turn the fans off leaving the heat on full and air drawn into the car through the movement of the car should draw heat in with less energy being used.

goldspanners

thescouselander wrote: »

Actually, the battery is only there to start the car and temporarily run some devices such as the radio while the engine is off. As soon as you start the engine the alternator takes the load for running anything electrical. If you were to disconnect the battery while the engine is running everything should keep working.

The heater in your car works off the hot coolant in the engine. If it wasn't used to heat the inside the heat would just be radiated outside anyway by the radiator. Of course the fan uses electricity but not that much so generally keeping warm wont cost you that much.

The rear de-mister uses a lot of current (around 30 amps). This puts strain on the alternator therefore the engine will have to do more work. I would suggest only using the de-mister when you need it.

Things such as radios don't use much power

Lights can use a lot especially if your car has a lot of them but as another poster has said safety has to come first so its not a good idea to turn them off to try and save money.

Air con works by directly taking mechanical power from the engine - this causes the engine to use more fuel.

is this meant to be a serious reply?
you are so misinformed,go and disconnect the battery in your car with the engine running and see what happens.
or i could tell you.
the basics of it is,the battery is there to complete the circuit,disconnect this = no power anywhere,fuel safety solenoid will shut off, ecu will shut down, alternator will not be gettign any feedback from battery, etc,etc... the list goes on.
in theory your car could run without a battery,like old cars with start handles,but there is so much electronics in your car these days,and even days gone by that the battery needs to be connected.
just to exagerate this a bit,if you have ever tried to jump start another car with a petrol car you will have noticed as soon as you connect the last jump lead the engine will start to labour (or fan belt will squeal) this is due to the extra load being put on to the engine via the higher amperage required out of the alternator which in turn equals more fuel being used.
so the short answer is yes,using any electrical item which is using power from the car it will use slightly more fuel,not enough to really notice though.(except a/c of course thats different)